Method for improving crystalline titanosilicate catalyst having MWW structure

ABSTRACT

A method for improving a crystalline titanosilicate catalyst having an MWW structure, characterized in that it comprises treating the crystalline titanosilicate catalyst having a MWW structure with a silylating agent.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 of International Application No.PCT/JP03/002289, filed Feb. 28, 2003, the disclosure of which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method for improving a crystallinetitanosilicate catalyst having an MWW structure. More specifically, thepresent invention relates to a method for improving a catalyst, whichmethod is capable of efficiently activating a crystalline titanosilicatecatalyst having an MWW structure.

BACKGROUND ART

Various crystalline titanosilicate catalysts are known and some of themare known as being effective catalysts for the production of epoxycompounds by epoxidation of olefins, the productions of phenol compoundsor polyhydroxyphenyl compounds by hydroxylation reactions, of benzene orphenol compounds, respectively, or the like.

In addition, the present invention relates to a crystallinetitanosilicate catalyst having an MWW structure. The MWW structure is aframework type code name specified by International Zeolite Association(IZA). A crystalline metallosilicate (zeolite) having an MWW structureis known as the name of MCM-22. Therefore a crystalline titanosilicatecatalyst having an MWW structure, which contains titanium (hereinafterreferred to as Ti) within the framework, is known as the name of Ti-MWW,or Ti-MCM-22, or the like.

Additionally, this crystalline titanosilicate having an MWW structure isalso known to be a useful material as a catalyst.

Generally, enhancing the activity of a catalyst can lead to reduction ofthe amount of the catalyst and thus reduction of the catalyst cost, andalso to lower the cost of reaction vessel by reducing its size, andtherefore further enhancement of the catalyst activity of the Ti-MWWcatalyst is also desired.

As a method of highly activating the Ti-MWW catalyst, a method ofincreasing the Ti content is known (e.g., Chemical Communication 897,(2001)), but it is known that a high Ti content with the Ti to Si(silicon) ratio being 1/40 or more deteriorates the crystallinity of theTi-MWW catalyst (e.g., Journal of Physical Chemistry B, 105, 2897,(2001)). In general, with a crystalline titanosilicate catalyst, poorercrystallinity is accompanied by lesser catalyst performance in somecases. As such, a novel method of highly enhancing the activity of acatalyst except for increase of Ti content is needed.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a method for improvinga catalyst, which method is capable of efficiently enhancing thecatalytic activity of a crystalline titanosilicate catalyst having anMWW structure.

In other words, the present invention relates to a method of improving acrystalline titanosilicate catalyst having an MWW structure,characterized in that it comprises treating the crystallinetitanosilicate catalyst having an MWW structure with a silylating agent.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples of the method for producing a crystalline titanosilicatecatalyst having an MWW structure include the following methods.

That is, there are known a method that involves contacting with TiCl₄ acrystalline aluminosilicate catalyst having an MWW structure(hereinafterreferred to as Al-MWW), and substituting aluminum (hereinafter referredto as Al) with Ti to incorporate Ti as described in U.S. Pat. No.6,114,551; a method of hydrothermal synthesis using a titanium alkoxideas described in Chemistry Letters 774, (2000); a method that involvesonce crystallizing, delaminating the layers of the crystal, therebycollapsing the crystal, and then incorporating Ti to crystallize againas described in Shokubai (Catalysts & Catalysis) 44, 6, 468, (2002); ora method of synthesis by means of the dry gel conversion process using atitanium alkoxide as described in the proceedings of the 88th CatalysisSociety of Japan (CatSJ) Meeting A”, 154, (2001).

It is preferable on account of a higher activity that a Ti-MWW catalystused in silylation is a Ti-MWW catalyst containing Ti having beenincorporated during crystallization.

The methods for preparing a Ti-MWW catalyst containing Ti having beenincorporated during crystallization include a method that involveshydrothermal synthesis through the use of a titanium alkoxide; a methodthat involves once crystallizing, delaminating the layers of theresulting crystals, thereby collapsing the crystal, then incorporatingTi, and crystallizing again; and the dry gel conversion method with atitanium alkoxide; and the like.

In addition, when a Ti-MWW catalyst is prepared using Al as for themethod in which TiCl₄ is made to contact with an Al-MWW catalystdescribed in U.S. Pat. No. 6,114,551, since the residual Al acts asacidity that induces a side reaction in some cases, a method withoutusing Al is preferable.

In the present invention, a crystalline titanosilicate having an MWWstructure, that is, a Ti-MWW catalyst is treated with a silylatingagent.

The silylating agents include, for example, silylamine compounds such as1,1,1,3,3,3-hexamethyldisilazane, (N,N-dimethylamino)trimethylsilane,N-(trimethylsilyl)imidazole or the like, chlorosilane compounds such astrimethylchlorosilane, t-butyldimethylchlorosilane or the like,acetamide compounds such as N,O-bis(trimethylsilyl)acetamide,N-(trimethylsilyl)acetamide, trimethylsilyldiphenyl urea,bis(trimethylsilyl)trifluoroacetamide, and the like. Particularlypreferred are 1,1,1,3,3,3-hexamethyldisilazane andtrimethylchlorosilane.

Methods of treating the Ti-MWW catalyst with the silylating agent may beany method that allows the catalyst to contact with the silylatingagent, and for instance, examples thereof include the following method.That is, the silylation treatment is carried out by mixing the catalystand the silylating agent. An organic solvent may be used for thetreatment, if necessary, and it may be conducted under heating, ifnecessary. Heating an complete the silylation treatment in a shortperiod of time. The treatment temperature is not particularly limited,but normally from 20° C. to 200° C. Usually, further filtration andwashing followed by drying provide the Ti-MWW catalyst treated bysilylation. Organic solvents that may be used, if necessary, for thetreatment include aromatic hydrocarbon compounds such as toluene,nitrile compounds such as acetonitrile, aliphatic hydrocarbon compoundssuch as n-heptane, ether compounds such as tetrahydrofuran, amidecompounds such as dimethylformamide, cyclic amine compounds such aspyridine, amine compounds such as triethylamine, and the like. Also,when a silylating agent containing chlorine such astrimethylchlorosilane is used, a basic organic solvent such as pyridineor triethylamine is preferably used.

The catalyst of which activity is enhanced by the present invention cansuitably be used for epoxidation reactions of olefins using hydrogenperoxide, or hydroxylation reactions of benzenes or phenol compoundsusing hydrogen peroxide. Epoxidation reactions of olefins using hydrogenperoxide can particularly suitably be used for the epoxidation reactionof propylene.

Methods of supplying hydrogen peroxide include a method of supplying ahydrogen peroxide solution produced in advance, a method of supplyingin-situ synthesized hydrogen peroxide from hydrogen and oxygen, and thelike. Methods of synthesizing hydrogen peroxide in the reaction system,in-situ, include a method of synthesizing hydrogen peroxide by usingtransition metal catalyst such as Pd(palladium), or Au(gold) forsynthesizing hydrogen peroxide from hydrogen and oxygen in-situ, mixedwith or supported on the Ti-MWW catalyst.

The aforementioned reaction can be carried out in the presence of anorganic solvent, if necessary. The organic solvent can also be used bymixing with an inorganic solvent such as water, or with an inorganiccompound in a supercritical state such as carbon dioxide in asupercritical state. The organic solvents that may be used include ahydrocarbon, a halogenated hydrocarbon, an alcohol, a ketone compound,an ether compound, an ester compound, a nitrile compound, and the like.Preferred organic solvents are nitrile compounds. A preferred nitrilecompound is acetonitrile.

In addition, the reaction methods using the activated catalyst of thepresent invention include a fixed bed flow reaction method and a slurryreaction method.

EXAMPLES Example 1

Treatment with a silylating agent was carried out using a Ti-MWWcatalyst having a Ti content of 1.0% by weight as determined by ICPemission spectrometry, prepared in accordance with the method describedin Chemistry Letters 774, (2000).

Silylation was conducted by mixing 3.4 g of1,1,1,3,3,3-hexamethyldisilazane, 50 g of toluene and 5 g of the Ti-MWWcatalyst and refluxing the mixture for 1.5 h. Further, after filtrationand washing, dried under reduced pressure at 120° C. to yield thesilylated Ti-MWW catalyst.

Then, a reaction was carried out using the resultant silylated Ti-MWWcatalyst. That is, a solution of H₂O₂: 5% by weight, water: 47.5% byweight and acetonitrile: 47.5% by weight was prepared with an aqueous60% H₂O₂ solution (product of Mitsubishi Gas Chemical Co., Inc.),acetonitrile and purified water. 12 Grams of the solution prepared and0.010 g of the silylated Ti-MWW catalyst were loaded into a 50 mlstainless steel autoclave. Thereafter, the autoclave was transferredonto an ice water bath, and was loaded with 10 g of liquefied propylene.Furthermore, the pressure was increased to 2 MPa-G with nitrogen. Thereaction was deemed started when 5 minutes passed after the autoclavehad been placed in hot water bath maintained at 40° C., the insidetemperature reaching about 35° C. One hour after the reaction starting,the autoclave was taken out of the warm water bath and sampling wasconducted. The analysis was carried out by gas chromatography. As aresult, the propylene oxide formation activity per catalyst weight was0.510 mol·h⁻¹·g⁻¹. The propylene oxide selectivity based on propylenewas 99.8%.

Example 2

A reaction and analysis were carried out in accordance with the methodin Example 1 with the exception that acetone was used instead ofacetonitrile.

As a result, the propylene oxide formation activity per catalyst weightwas 0.363 mol·h⁻¹·g⁻¹. The propylene oxide selectivity based onpropylene was 99.2%.

Comparative Example 1

A reaction and an analysis were carried out in accordance with themethod in Example 1 with the exception that an unsilylated catalyst ofthe catalyst used in Example 1 and thus the Ti-MWW catalyst that was notsilylated was used.

As a result, the propylene oxide formation activity per catalyst weightwas 0.463 mol·h⁻¹·g⁻¹. The propylene oxide selectivity based onpropylene was 99.9%.

Comparative Example 2

A reaction and analysis were carried out in accordance with the methodin Example 2 with the exception that an unsilylated catalyst of thecatalyst used in Example 2 and thus the Ti-MWW catalyst that was notsilylated was used.

As a result, the propylene oxide formation activity per catalyst weightwas 0.230 mol·h⁻¹·g⁻¹. The propylene oxide selectivity based onpropylene was 98.4%.

INDUSTRIAL APPLICATION

As described above, the present invention can provide a method forimproving a catalyst, capable of efficiently activating a crystallinetitanosilicate catalyst having a MWW structure.

1. A method for improving a crystalline titanosilicate catalyst havingan MWW structure, comprising treating the crystalline titanosilicatecatalyst having a MWW structure with a silylating agent to produce asilylated crystalline titanosilicate catalyst having a MWW structure. 2.The method according to claim 1, wherein the crystalline titanosilicatecatalyst having an MWW structure is a catalyst containing Ti having beenincorporated during crystallization.
 3. The method according to claim 1,wherein the catalyst is a catalyst used for epoxidation reaction of anolefin with hydrogen peroxide or a catalyst used for hydroxylationreaction of a benzene or a phenol compound with hydrogen peroxide. 4.The method according to claim 1, wherein the catalyst is a catalyst usedfor the epoxidation reaction of propylene with hydrogen peroxide.
 5. Themethod according to claim 1, wherein the catalyst is a catalyst used fora reaction utilizing a nitrile compound as a solvent.
 6. The methodaccording to claim 2, wherein the catalyst is a catalyst used forepoxidation reaction of an olefin with hydrogen peroxide or a catalystused for hydroxylation reaction of a benzene or a phenol compound withhydrogen peroxide.
 7. The method according to claim 2, wherein thecatalyst is a catalyst used for a reaction utilizing a nitrile compoundas a solvent.
 8. The method according to claim 2, wherein the catalystis a catalyst used for the epoxidation reaction of propylene withhydrogen peroxide.